test(vulkan): honor storage buffer offset alignment

[Colin-Hayes]

Summary

• use the existing 4096-byte test alignment for nonzero Vulkan storage-buffer descriptor offsets
• retain sentinel coverage before and after the bound tensor range
• rename the test to describe aligned offset binding instead of nonexistent multi-workgroup coverage

Why

The Qualcomm Adreno X1-45 driver reports minStorageBufferOffsetAlignment = 64. The previous test bound an eight-element FP32 tensor at byte offset 32, so the backend correctly rejected the submission as incompatible before dispatch. Intel ANV's less restrictive alignment did not expose the test assumption.

This PR is stacked on #182 and targets its vulkan/ffi-8 branch.

Validation

On Qualcomm Adreno X1-45 GPU, Vulkan 1.3.295, Windows ARM64:

cargo fmt --check
$env:VIRTIO_ACCEL_VULKAN = "1"
cargo clippy -p virtio-accel-vulkan --all-targets -- -D warnings
$env:VIRTIO_ACCEL_VULKAN_REQUIRE_DEVICE = "1"
cargo test -p virtio-accel-vulkan -- --nocapture

The Vulkan crate suite passes: 30 tests passed, 0 failed, and the manual performance test remains ignored.

The merge-base changed after approval.

[Copilot]

🟢 Approval recommended

The change is confined to test logic, aligns descriptor offsets to avoid known Vulkan driver constraints, and preserves/strengthens the existing guard-region assertions.

Pull request overview

This PR updates the Vulkan integration test suite to ensure storage-buffer descriptor bindings use a nonzero offset that is aligned to Vulkan’s minStorageBufferOffsetAlignment, preventing spurious backend rejections on stricter drivers (e.g., Qualcomm Adreno) and renaming the test to match its actual coverage.

Changes:

• Rename the test to reflect aligned offset binding coverage rather than multi-workgroup behavior.
• Bind input/output storage buffers at a nonzero, aligned byte offset and size buffers to include guard regions.
• Preserve sentinel verification before and after the bound tensor range while writing/reading with the new offset.

File summaries

File	Description
crates/virtio-accel-vulkan/tests/vulkan.rs	Updates the offset-binding test to use aligned nonzero descriptor offsets with padded buffers and sentinel checks.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 0
• Review effort level: Lite

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.